P1383: EXTRAMEDULLARY RELAPSE OF ACUTE MYELOID LEUKEMIA AND ACUTE LYMPHOBLASTIC LEUKEMIA AFTER ALLOGENEIC HEMATOPOIETIC STEM CELL TRANSPLANTATION - A SINGLE-CENTER EXPERIENCE
Authors: F. Vasconcelos, D. Rochate, E. Couto, P. Coelho, L. Leite, R. Branca Ferreira, C. Pinho Vaz, A. Campos
Journal: HemaSphere (2022)

Background: Acute leukemia relapse after allogeneic hematopoietic cell transplant (allo-HCT) is challenging. Allo-HCT is a potentially curative treatment for acute myeloid leukemia (AML) and Acute lymphoblastic leukemia (ALL). Extramedullary relapse (EMR) can occur in various extramedullary tissues such as the central nervous system (CNS), breast, bone, testis, and skin, and data on EMR after allo-HCT is limited. EMR is a long-term complication of stem cell transplantation with a poor prognosis. Aims: To characterize EMR in the setting of allo-SCT for AML and ALL. Methods: Retrospective analysis of relapsed patients (pts) submitted to allo-SCT for AML and ALL at our center from January 2011 to December 2021. Disease characteristics, type of transplant, outcome-related data were collected from clinical files. All cases were confirmed by biopsy. Survival was estimated by Kaplan-Meier method. Results: Between 2011 and 2021, three hundred and seventy one AML and ALL pts were transplanted in our center. After the allo-HCT, 106 patients had a relapse, of which 86 were bone marrow (BM) relapses and 20 were EMR. Among the 20 EMR pts there were: 14 males and 6 females with a median age of 38 (range, 19 – 59) years. Of these, 13 had AML (AML Not Otherwise Specified (NOS) (n=9), AML with myelodysplasia-related changes (n=2), Myeloid sarcoma (n=1) and AML with recurrent genetic abnormalities: AML with inv(16)(p13.1q22) (n=1)), 7 had ALL: ALL-B (n=4), ALL-T (n=2), ALL-B with recurrent genetic abnormalities t(9;22)(q34;q11) (n=1). Twelve pts had a related donor, 1 pt had an HLA-haploidentical donor and 7 pts had a non-related donor (NRD). All patients with NRD were transplanted with a myeloablative regimen. Among patients with related donors, 11 were transplanted with a myeloablative regimen and 2 with a non-myeloablative regimen. The EMR site varied widely, including the CNS (n=3), skin or soft tissue (n=3), bone (n=1), testis (n=2), lymph nodes (n=2), breast (n=3). Multiple sites of EMR (≥2) were observed in 6 patients. Among the 86 BM relapsed pts there were: 42 males and 44 females with a median age of 43 (range: 1-66) years. Of these, 57 had AML (AML Not Otherwise Specified (NOS) (n=45), AML with myelodysplasia-related changes (n=12). Twenty nine pts had ALL: ALL-B (n=19), ALL-T (n=3), ALL-B with recurrent genetic abnormalities t(9;22)(q34;q11) (n=7). 40 pts had a related donor, 1 pt had an HLA-haploidentical donor and 45 pts had a non-related donor (NRD). Thirty seven patients with NRD were transplanted with a myeloablative regimen and 8 with a non-myeloablative regimen. Among patients with related donors, 22 were transplanted with a myeloablative regimen and 19 with a non-myeloablative regimen. Relapse free survival (RFS) of EMR pts was 12 months (CI 95%: 0-26.6) and the median overall survival (OS) after EMR was 4 months (CI 95%: 0-13.2) RFS of pts with BM relapse was 2 months CI 95%: 1.1-2.9) and the median OS after BM relapse was 3 months (CI 95%: 1.5-4.4). Summary/Conclusion: Although our study includes a small number of pts experiencing EMR, results show that EMR was more frequent in men, AML NOS, and EMR is frequent in multiple sites (6 of 20 patients). The median OS after EMR was 4 months, the same reported in the literature. Results suggest that EMR has a different behavior from BM relapse, associated with better RFS and OS.